Shapes can be defined and classified according to their attributes.

Children need to go beyond the use of superficial shape labels to recognizing and specifying the defining attributes of shapes. As children sort and classify shapes with knowledgeable others, they become aware of rules about shapes, such as that a triangle has three sides and three angles (corners), that a cylinder has a rounded form with two flat ends that are in the shape of a circle, or that a sphere has only one continuous curved side. That these sorts of precise distinctions can be made is not immediately obvious to young children; for this reason, it is important that teachers design activities to demonstrate this.

Geometry and measurement are often difficult topics for young math students. Doug Clements argues that part of this problem stems from classroom materials that are inexact and misleading. “At its fundamental base, mathematics is about precision of reasoning and thinking.”